Distribution and genetic diversity of the invasive clinging jellyfish Gonionemus vertens on Nantucket and Muskeget Islands

Report submitted in fulfillment of a 2016 Nantucket Biodiversity Initiative grant The goals of this project were to document the distribution of the invasive clinging jellyfish Gonionemus in Nantucket and Muskeget Islands and to analyze its regional population genetic diversity. Gonionemus is native to the north Pacific coasts and was first documented locally in Woods Hole and Muskeget Island in the early 20th century. This form of Gonionemus was not associated with painful stings, despite frequent handling by scientists and collectors. An invasion of a more toxic form of Gonionemus appears to have occurred in the late 1980s in the Cape Cod region. Several individuals have reported Gonionemus stings in parts of Waquoit Bay (Cape Cod) and Martha’s Vineyard, but none to date have been recorded from Nantucket. Jellyfish surveys were coordinated with Mary Carman (WHOI) who conducted a parallel NBI study on the distribution and abundance of invasive tunicates in eelgrass meadows on Nantucket and Muskeget Islands. Despite extensive searching, no Gonionemus were found on either Nantucket or Muskeget. However, a broader genetic analysis of regional Gonionemus populations indicated the presence of multiple lineages, one of which is shared with well-known toxic populations in the Sea of Japan. The unique lineages indicated that native Gonionemus diversity also likely exists in the area. While no Gonionemus were found on Nantucket or Muskeget, it is possible that Gonionemus may arrive in the near future. The life cycle of Gonionemus includes minute asexual stages which could easily hitchhike on ship hulls and other vectors. Monitoring eelgrass habitats will facilitate early detection, so that mitigation measures can be most effectively applied